The sound barrier

[Juha]

Soren

Quote " As a matter of fact I've never heard or read about high stick forces in the Me-262, from all that I have read about the a/c the controls were light and well harmonized at all speeds."

Please look Hohun's message #36 in this very thread, or better still the Flight Journal Winter 2000 which HoHun gives as the source. Same can be found from Brown's Wings of the LW p. 66. Brown's own dives on the 262 up to a max Mach 0.84 fully confirmed all Lindner's observations.

From the latter "On the strength of these tests [flown by Lindner, Juha] , the LW pilots had been instructed not to exceed airspeed of 960 km/h below 8 000m, more than 900 km/h being considered inadvisable above that altitude…the trimmer should not be used as an aid for recover"

Juha

 

[kool kitty89]

Thanks Juha, HoHun's post makes the characteristics very clear.

Regarding the resulting control forces, here is an interesting comment by Eric Brown (from Flight Journal Special Winter 2000):

"In the dives from 30,000 ft, the nose started to drop at Mach 0.83 and a 30-pounds pull was required to maintain the 25-degree dive angle. As the Mach number increased a violent buffeting set in, and the aircraft became progressively nose-heavy, so a pull force of about 100 pounds was necessary at Mach 0.86 to keep the dive angle constant."

His dives were carefully prepared in order to measure the maximum possible Mach for the Me 262, including carefully pre-setting the optimum dive trim on the ground.

Regards,

Henning (HoHun)

It seems that the controls aren't getting "stiff" as much as the aircraft was getting nose heavy (due to a movement in center of lift at critical mach). It would also seem that at these speeds the tailplane's critical Mach number hasn't yet been exceeded. So it may have been possible that trimming the tailplane to counter this (restoring proper trim) would have left elevator authority intact as well. (at least until the tailplane reached critical Mach)

That would make sense too, as the ailerons and rudder were still effective at these speeds.



Bill, when the tailplane's critical Mach number is exceeded, will the resulting shock wave (and turbulence) definitely result in loss of elevator control? (regardless of stick forces -or control boost- applied)
Or are there other factors in the tailplane's characteristics that could effect this?

My understanding is that when Mcrit is exceeded a shockwave develops (first on the upper surface, later on the lower) and the control would be lost once the shock was significant enough to make the airflow separate before reaching the control surface(s).

Also, will the elevator become functional again once the entire tailplane has gone supersonic? (assuming sufficient control forces -ie boosted elevator controls)

 

[Juha]

KK
As Soren rather childishly asked Bill to provide a link to the book Bill used as his source I gave the HoHun's message as an independent proof to Bill's message, because HoHun's message is a short version of Bill's rather extensive message #225. And so it has to be, because Brown's comment is a quote from Lindner's report. I only added that Brown's own dives on the 262 up to a max Mach 0.84 fully confirmed all Lindner's observations. And same time added another source, Brown's book, from where to check Lindner's observations.

Juha

 

[Soren]

Juha, how is asking for sources childish when I am asked for the same as-well ? Bill asked for sources, I provided the Me-262 POH.

 

[pbfoot]

Is there really such a thing as a POH for LW Aircraft, not according to my sources who say the data on the aircraft was "beaten into them in class" and says all the operating notes or POH was post war creations I have no reason to doubt my sources.

 

[Soren]

I think I'm just gonna repeat what I'm trying to point out here:

I say the Me-262 quite clearly broke the sound barrier because as Mutke explains the heavy vibrations and uncontrollable pitch down his a/c exhibited while in the transonic region suddenly seized and a smooth ride followed while still in the dive, after which he shut his engines and started to trim the tail plane to recover from the dive (The all moving tailplane is what allowed him to recover from the dive as shockwaves rendered the elevators ineffective), shortly after the vibrations started again. This to me is a clear sign that he went supersonic. And studies done in Germany in 1999 prove that it was possible for the Me-262 to go supersonic, but it was risky and damage to the a/c was almost assured, and depending on the quality of the workmanship of the airframe it could come apart in the attempt as-well.

Further proof that the Me-262 either went supersonic or came extremely close to it is the British claims that the Spitfire, a propeller driven a/c, reached Mach 0.9 in dives. The claim is substantiated by the fact that the speeds were recorded to be viewed afterwards. The Spitfire featured no wing sweep and being a propeller driven a/c it had absolutely no thrust at such high speeds, so to explain why the a/c was capable of such a speed it is claimed that it is the unusually thin airfoil which gave the a/c its high Mach number.

Keeping the above in mind it should be mentioned that the Me-262 not only featured a thinner wing than the Spitfire but also wing sweep, and even more crucial is the fact that the Me-262 is a Jet and thus has available a lot of thrust at high speeds. Furthermore the Me-262 is a much cleaner a/c than the Spitfire.

In level flight the average Me-262 achieved a top speed of Mach 0.77 to 0.79 at a height of 6km (The British established the top level speed to be 900 km/h in several recorded flights).

So there is absolutely no doubt in my mind that the Me-262, along with the Me-163 F-86 Sabre, broke the sound barrier before Chuck Yeager in his X-1 craft.

In short, IF the Spitfire could reach Mach .9 in a dive, a speed at which the prop acts as nothing but a speed brake, then you can pretty sure that the Me-262 could go even faster in a dive as not only is it a jet but it's cleaner, got a thinner wing and features some wing sweep.

So the only WW2 a/c which could've gone supersonic or come closest to it is the Me-262, Me-163 or Go-229 prototype.

 

[Soren]

Is there really such a thing as a POH for LW Aircraft, not according to my sources who say the data on the aircraft was "beaten into them in class" and says all the operating notes or POH was post war creations I have no reason to doubt my sources.

What are your sources exactly ? The reason I'm asking is that I have both the LW Ta-152H Me-262 POH, the Ta-152's was printed in January 1945.

 

[Juha]

Soren
in his message #225 Bill gave his source, Stormbird Rising, with page number ,but in Your message #234 you still asked
Quote:"Give me a link to Lindners debriefing and Baur's verification Bill cause I can't find it."

That's the reason to my comment.

On early jets vs late propeller planes
And how You explain that in RAE's tests its High Speed Flight Section found out that Spitfire PR XI could dive faster than for ex Meteor or Vampire? The critical point isn't trust, look the table on Mach .89 dive of PR XI, the dive angle was at its max a bit over 45 deg. The limiting factor was the ability of pilot to pull the stick, at 0.89 the pull needed on PR XI was the same 110lb than Lidner tells was needed on 262 at 0.86. Brown tells that for him the max on PR XI was .86 because of his small statue, he didn't have as much muscle power as Tobin? or Martindale and maybe he left a bit more margin than those other two when he began his pull out.

Juha

 

[Soren]

Juha,

A Meteor Vampire isn't a Me-262, both featur thicker wings, lower thrust, minimal to no sweep.

 

[Juha]

Soren
otherwise true but Meteor III had two Rolls-Royce Derwent I with 900 kgp trust each, so so much to your "even more crucial is the fact that the Me-262 is a Jet and thus has available a lot of thrust at high speeds."

Juha

 

[drgondog]

Thanks Juha, HoHun's post makes the characteristics very clear.

Bill, when the tailplane's critical Mach number is exceeded, will the resulting shock wave (and turbulence) definitely result in loss of elevator control? (regardless of stick forces -or control boost- applied)
Or are there other factors in the tailplane's characteristics that could effect this?

When the airspeed gets to the point of transonic there will be a formation of the shockwave at approximately t/c max. It will tend to cause a separation of flow aft of it almost immediately which will render any control surface immersed in the wake ineffective. Note that I am talking about elevator/trim tabs not the tailplane. It could still be effective if boosted in this case so long as IT is not, in turn, immersed in wake turbulence.

My understanding is that when Mcrit is exceeded a shockwave develops (first on the upper surface, later on the lower) and the control would be lost once the shock was significant enough to make the airflow separate before reaching the control surface(s).

Yes but in the case of the tailplane, depending on its 'attitude', the shock should start on the bottom surface. In this discussion it is more likely to form on bottom as the incidence angle is 'down' while the pilot is trying to pull up - It is acting as an 'upside down' airfoil at this point and the higher velocity is on the bottom.

Also, will the elevator become functional again once the entire tailplane has gone supersonic? (assuming sufficient control forces -ie boosted elevator controls)

Yes.

I feel (no proof) that the issue at .82-.86 M was that the tailplane did not have enough boost to deflect down with normal pilot strength to overcome the loads imposed by the Down pitching moment in the transonic initiation - and further suspect that existing mechanical advantage of the tailplane was designed with the structural integrity in mind.

Hence the 'Do not Use Trim' directive - except in absolute emergencies.

The additional trim at those speeds would probably be the factor that caused several 262s to crash in dives although I have not seen any reports of a tail separating to validate that speculation - so, it is pure speculation on my part

 

[drgondog]

I think I'm just gonna repeat what I'm trying to point out here:

I say the Me-262 quite clearly broke the sound barrier because as Mutke explains the heavy vibrations and uncontrollable pitch down his a/c exhibited while in the transonic region suddenly seized and a smooth ride followed while still in the dive, after which he shut his engines and started to trim the tail plane to recover from the dive (The all moving tailplane is what allowed him to recover from the dive as shockwaves rendered the elevators ineffective), shortly after the vibrations started again. This to me is a clear sign that he went supersonic. And studies done in Germany in 1999 prove that it was possible for the Me-262 to go supersonic, but it was risky and damage to the a/c was almost assured, and depending on the quality of the workmanship of the airframe it could come apart in the attempt as-well.

Babble.. speculation, supposition, no facts

Further proof that the Me-262 either went supersonic or came extremely close to it is the British claims that the Spitfire, a propeller driven a/c, reached Mach 0.9 in dives. The claim is substantiated by the fact that the speeds were recorded to be viewed afterwards. The Spitfire featured no wing sweep and being a propeller driven a/c it had absolutely no thrust at such high speeds, so to explain why the a/c was capable of such a speed it is claimed that it is the unusually thin airfoil which gave the a/c its high Mach number.

The Mustang dive trials were stopped at ~.85 because the pilot feared for his life based on observations of the ammo door deflections and the vibration he was experiencing - not because he achieved terminal velocity. It is safe to say that both the 262 and Spit exceeded the Mustang dive speeds.

It is reasonable to speculate, that if the 262 could overcome the pitch down issue with breaking the bird structurally, that is should exceed the Spit in a dive.

It is not reasonable to assume the 262 could overcome the pitch down moment until proven otherwise from .85 up, and also from .9+ back to below .85 M. That transonic issue works both directions

Keeping the above in mind it should be mentioned that the Me-262 not only featured a thinner wing than the Spitfire but also wing sweep, and even more crucial is the fact that the Me-262 is a Jet and thus has available a lot of thrust at high speeds. Furthermore the Me-262 is a much cleaner a/c than the Spitfire.

You have any data on shock wave issues at the inlet for both engine nacelles and subsequent proof that the engine does not flame out? Or that the Me 262 could exceed the speed of sound in a terminal unpowered dive?


So there is absolutely no doubt in my mind that the Me-262, along with the Me-163 F-86 Sabre, broke the sound barrier before Chuck Yeager in his X-1 craft.

Soren, the uninformed and irrational frequently exist in a state of absolute confidence in their personal point of view. Your rationale and fact base are adequate to support your belief system but fail to meet the test of fact based science. However, your zeal and enthusiasm in the pursuit of the ludicrous is to be commended. You are a triumph of the uncluttered mind.


In short, IF the Spitfire could reach Mach .9 in a dive, a speed at which the prop acts as nothing but a speed brake, then you can pretty sure that the Me-262 could go even faster in a dive as not only is it a jet but it's cleaner, got a thinner wing and features some wing sweep.

IF your thesis was that a Me 262 was faster in a dive, and speculated that it might approach the speed of sound given the possibility of overcoming certain technical issues - you would not have sounded so silly as you just did by unequivocally claiming that Mutke broke the sound barrier first.

So the only WW2 a/c which could've gone supersonic or come closest to it is the Me-262, Me-163 or Go-229 prototype.

The point is - there is a remote possibility that Mutke did exceed the speed of sound in an airplane that Willy M directed to be flown below .86 M.

There is a remote possibility that the study you referenced did prove that the stability and control design features of the Me 262 were sufficient to proceed into a vertical dive and at that point remove the pitch down moment before it became a cloud of aluminum particles.

There is a remote possibility that the study proved that the tail structure was in fact adequate to enable the forces required to pull the a/c out of a dive from 1.0 Mach or survive the continued pitch down forces after .86 M.

There is a higher possibility that the study proved that the Me 262 could reach a terminal velocity > 1.M after the engine flamed out or prove that the inlet geometry was adequate to prevent shock stall of the Jumo engine.

That would be an analytical approach to support a 'possibility'

Nothing factual supports the reality.

 

[Soren]

Babble.. speculation, supposition, no facts

Babble my ass Bill, Mutke's account is as it is, it isn't babble, so if you don't believe the details of it then why not just be open and call the man a liar ?? And the study done in Germany DID conclude that the Me-262 was capable of breaking the sound barrier in a steep dive, so again not babble, just facts, just how you like it right ?

 

[Soren]

Soren, the uninformed and irrational frequently exist in a state of absolute confidence in their personal point of view. Your rationale and fact base are adequate to support your belief system but fail to meet the test of fact based science. However, your zeal and enthusiasm in the pursuit of the ludicrous is to be commended. You are a triumph of the uncluttered mind.

Why is it you have to be an ass toward others Bill? Have I called you names or anything else in this entire debate ?? NO! So why is it you insist on being childish and calling others names ? You love to do this things when you get overconfident in yourself. Stick to the subject, refrain from childish name calling, base your own conclusions on facts instead of requiring them from others.

Babble, ha!

 

[drgondog]

Babble my ass Bill, Mutke's account is as it is, it isn't babble, so if you don't believe it then why not just be open and call the man a liar ?? And the study done in Germany DID conclude that the Me-262 was capable of breaking the sound barrier in a steep dive, so again not babble, just facts, just how you like it right ?

I didn't say Mutke's account was 'babble' - I said Your entire dissertation was babble. I have never said that I disbelieve Mutke's impressions - I just don't believe he exceeded Mach 1.

Produce the report - your say so and your interpretation of engineering concepts are demonstably below par and frequently absent facts.

Remember 'Suction=Drag' was your interpretation of Lednicers report? Do you recall saying the '262 control forces are light at all speeds"? Do you recall saying that the shock wave on the elevator started at the trailing edge?

Do you recall your interpretation of the USAAF recount of 'snaking and hunt in the horizontal' as trash and associated that to 'only one or two' based on quality issues?

As to not insulting me - how many times have you said I was a 'liar' or (gasp) 'an amateur' with respect to performance and aerodynamics - or completely 'clueless'?? or any of many others on this forum who challenge your strange belief systems.

Go back just through this Thread and see what you find?

 

[Soren]

LoL Bill, stop relying on past events, I haven't called you anything for a LOOONG time, and the times I did call you something it wasn't until after YOU had started by calling me god knows what. Go back and read yourself if you dont believe me. You love provoking people by calling them names.

Do you recall saying that the shock wave on the elevator started at the trailing edge?

Sure, by mistake, hence why I said the exact opposite at the beginning of this thread. Is that STILL too much to comprehend for you Bill ?

 

[Soren]

Do you recall your interpretation of the USAAF recount of 'snaking and hunt in the horizontal' as trash and associated that to 'only one or two' based on quality issues?

Nope that's a lie Bill, I relied on Hans Fey who says:

 

[pbfoot]

What are your sources exactly ? The reason I'm asking is that I have both the LW Ta-152H Me-262 POH, the Ta-152's was printed in January 1945.

The pilots

 

[drgondog]

LoL Bill, stop relying on past events, I haven't called you anything for a LOOONG time, and the times I did call you something it wasn't until after YOU had started by calling me god knows what. Go back and read yourself if you dont believe me. You love provoking people by calling them names.



Sure, by mistake, hence why I said the exact opposite at the beginning of this thread. Is that STILL too much to comprehend for you Bill ?

Insults From This week - Oct 18
"Bill,

The study no doubt took in to account the structural integrity of the a/c, infact that is mentioned, otherwise it wouldn't be a serious study. However it was a serious in depth study Bill, not some amateur's go at trying to resolve some issue by assuming this and that.

And just because I don't have the report doesn't mean it isn't valid Bill, don't try to muddy the waters by suggesting such nonesense. I don't have to prove why the Me-262 could go supersonic in a dive, professional aerodynamicists have proven that it could by taking all aspects into account, otherwise it wouldn't be a serious study. So I am truly sorry Bill but I believe the professionals who took the time to study the issue in its entirety more than some hunch by a retired aero engineer.

So stop the twisting and turning and accept what the professionals have said on the subject, or are you suggesting you know better than them ? I aint.

"Bill that is a lie, I never mentioned the Mustang, all I said was I doubt that the Spitfire ever reached Mach .9 in a dive, I think Mach .82 seems a lot more reasonable.

Fabricating stuff definitely doesn't bolster your own credentials Bill."

For your comments on the USAAF Report that the 262 had a Tendency to Hunt

From Post 136 this week

"Only a few exhibited this behavior Bill, not all, which can be attributed to the varying degree of quality the a/c were being built to depending on which factory they came from

From Today on the snaking issue - and you still haven't acknowledged either the POH you sourced or Kapitan Kurt Wendel's contradiction to your POV on this

"I have a source for the fact that only a few Me262's exhibited the tendency to hunt: Me-262 test pilot Hans Fey, Allied Report, the site I referenced, written in big bold black letters."


From this week on Professional Aero's and the standards they should meet in their opinions to conform to your reality


"First of all Willy wasn't the designer, and secondly all that was concluded was that at Mach .86 the Me-262 would enter an untrollable pitch down dive, the increasing negative G-forces eventually breaking the a/c apart."

More on your judgement of Willy M. knowledge of his prize creation

"But how does that verify one comment of his on the Me-262 ? Like I said he didn't design the a/c and he wasn't part of the research team, so his total technical knowledge on the Me-262 would've been limited as he didn't work with the a/c every day."

So much for Willy Messerschmidt being an unreliable opinion. I hope the Professionals that performed the Professional Study exceeded Willy's talents in order to make your short list.


From some of your earlier posts in which you exhibited your own professional credentials

"It has been solidly confirmed by studies done in Germany that the Me-262 was perfectly capable of breaking the soundbarrier.

"The Me-262 would be uncontrollable in pitch after 1,100 km/h, so diving to Mach 1 and surviving it would've been a great feat!"

"The problem which could occur was as KK describes if the pilot failed to stop the negative G the a/c automatically started to generate above .86+ Mach by trimming the tailplane.

"Regarding the discussion link you provided earlier: It is completely incorrect that the Me-262's airframe couldn't sustain the stress of a Mach 1 dive, as proven in studies done in Germany in 1999. That needs to be made clear."

and more

"The only way to get out of the negative G dive the Me-262 would start after 1,100 km/h was to utilize the movable horizontal stabilizer, the elevators and therefore also trim tabs being rendered useless because of turbulent flow.
"
A normal Me-262 in 1945 wasn't of very good quality Juha, so obviously there would be structural issues. But a Me-262 built to the standards of those made in mid 44 would be perfectly capable of breaking the soundbarrier without breaking apart. However, and yes I read the report as-well, distortion of the wings and popped rivets are to be expected.
"


"I aint talking down to you Waynos, I'm just telling you that the tests didn't conclude anything about the Me-262's airframe not being able to take the stresses of a Mach 1 dive. And the airframe could take it as established in studies done in 1999. The problem was the pitching down above 0.86 Mach, something which could only be corrected by use of horizontal stabIt is a case a false speed readings that's all, a known issue at very high subsonic speeds. The Spitfire couldn't go that fast without falling apart.ilizer trim, which I have heard the British weren't aware of, I think Hohun knows about this.

There are no miracles in physics mate, all things in aero can be measured, just like your sig lets us know."


You may have a memory retention problem on the topics and your different positions depending on who 'caught you'.

Regarding insults, you may simply have a different standard for insults for different people.

 

[kool kitty89]

Guys, I found something interesting in the previous article I mentioned (with the riveted elevator tabs) Gas Turbines Also, on the tabs, it turns out this article is based on US captured examples of Me 262's.

But in any case, (on pg 21 of the article) there's some very interesting info on the controls which largely explains the discrepancies in reports of the high speed characteristics. It seems early models had controls that became very stiff at ~500 mph, an extended stick was proposed to correct this. However, this doesn't apear to have ever been carried out; instead an additional large mass balance was fitted which seems to have solved the problem.

Also, I'll double check, but neither "stiff controls" or directional snaking were experienced in the Wright field test, in fact iirc it was praised for its stability at high speed. (in shallow dives) Snaking wasn't mentioned either iirc.



And Bill, in a straight down 90 degree dive, there will be no pitch down behaivor, so that wouldn't be an issue.


Soren, on the comparison to the Spitfire, in the dive trials, the Spit was fitted with al fully feathering prop to avoid overspeeding, minimise propeller related compressibility issues, and minimize drag experienced at high speed.
The Me 262 would indeed still have thrust available at speeds where the Spitfire will have none (though both will be relying mostly on their weight). However, when the air ingested by the engines reaches supersonic speed, they will stall and flame out. (as Mutke experienced iirc) At this point the a/c is relying entirely on its weight alone for thrust. (although the engines had only been providing ~15-18% total thrust in a vertical dive)

Also, I retract my statement about the Spitfire being necessarily terminal at .89 Mach. It would be above its wing's Mcrit (for all sections much greater than ~10%) but given the thin tailplane the elevator may very well be fenctional. Additionally, while "tuck" is usually experience when an a/c's wing's critical mach number is exceeded, this isn't always the case (ie F-84 does the exact opposite) and the extremety of this characteristic veries as well. Assuming there is a tuck, it may be weak enough to counter with the stick or (if controls are too heavy) trim.

The critical Mach of the Spitfire's root section is probably ~.8 and increases as it tapers outward. (at 10% it should be arround .9 Mach) Due to the thicker section, the P-51D probably initially exceeds Mcrit of the wing somewhere arround .7-.75 mach. (iirc the earlier P-51's wing was somewhat thinner in section, as was the P-51H's)